Leveling device for raising platforms



Aug. 16, 1949. H, VO'SKAMP 2,479,089

LEVELING DEVICE FOR RAISING PLATFORMS Filed Feb. 7, 1947 2 sheets-sheet 1 Aug. 16, 1949. H, VOSKAMPv 'i 2,479,089

LEVELING DEVICE FOR RAISING PLATFORMS Filed Feb. 7, 1947 2 sheets-sheet 2 HERMAN VOJHAMP Patented Aug. 16, 1949 LEVELING DEVICE Fon RAISING PLATFORMS Herman Voskamp, Jutp'haas, Netherlands;v as" signor to Jan Jongerius Nl VA., Utrecht, Nether- Y lands Application February 7, 1947, serial No. 727,213

" In the Netherlands December 1,1943y section 1, Public Law 69o,- August s, 1946 Patent expires December. 1, 1963 (o1. fio-fsm n 4 Claims.

For the purpose of lifting loads, for instance, motor cars, lifting members, so called raising platforms, are known, in which said member is supported by a supporting post (column) vadaptn ed to be projectedV hydraulically or pneumatically. If veryheavy loads are to be lifted, two or more supporting posts are required for the platform. In lifting devices of this type it is difficult for the platform to be kept in a horizontal position during its movement, especially when the loadis not equally divided over the supporting posts.

The invention has for its object to provide a raising platform of the kind referred to having two or more hydraulic orpneumatic supporting posts and in which said difficulty is avoided.v

The invention consists in this, that a controlling device, adapted automatically to keep thev platformv in its horizontal position, is provided for eachsupporting post or for each of the outer` posts of more than two aligned posts, each of said devices comprising two valves inserted in series inthe liquid conduit connected to the active cylinder space. of thecorresponding supporting post, of which valves the rst, as seen in the direction in which the liquid is supplied, is operated bythe difference of pressure existing between two points of said conduit or between a point of 1 said conduit and a point of an air-duct connected toV said conduit, and the second is operated in dependency of the position of the platform relative to the corresponding supporting post, in such manner, that during movement of the platform the cross sectional area of the liquid conduit of each post moving too rapidly or too slowly is reduced or increased, respectively. The controlling devices operate so that, if the platform assumes an inclined position, the supply of liquid to or the ldischarge thereof from the supporting posts is controlled in such a manner that the posts moving too` rapidly are checked and the posts moving too slowly are accelerated, until the platform has resumed its horizontal or almost horizontal position.

With a view to ensuring the aforesaid automatic controlling action, the liquid conduit interthe. retraction of the corresponding post, the

cross-sectional area of the opened branch being y controlled by the second valve. Preferably, the

valves are constituted as Icylindrical slide valves,

of whichV the first is exposed to the pressures obtaining at two pointsl of the liquid conduit orthe 2 liquid-air conduit and is loaded by springs tendingto keep it inA its central position, the second being mechanically coupled to the platform, which is hinged to the corresponding supporting post.

In order to ensure a suicient dilerence of pressure for the control of the rst valve, it isA advisable, to provide a preferably adjustable throttle in that part of the conduit, in Which the difference of pressure is to be produced.

According to the invention, each supporting post may consist of a -cylinder and a hollow plunger cooperating therewith, the plunger space f communicating withthe working cylinder space through a liquid conduit fitted with the controlling device. In that case, the controlling device may be mounted on top of the plunger. supporting postsare Ydriven pneumo-hydraulically, the hollowvplunger of each post may be partially yfilled with liquid and connected to a compressed airdelivery conduit at a level above thatrof the liquid. During projection of the supportingpost, the liquid is thus urged from the hollow plunger Ainto the Working space of the cylinder.

These and other features of the invention will be elucidated hereinafter with reference to the drawing, in which:

Fig. 1 illustrates in diagram a sectional view of a part of a raising platform having a platform supported on two or more supporting posts, Vof which one only is shown, and

Fig. 2 shows on an enlarged scale a sectional view rof the controlling device .of the supporting post according to Fig. 1.

Fig. 3 is an elevational View of the upper structure of the raising platform according to Fig. 1, said platform being in an inclined position.

Figs. 3a and 3b show on a larger scale the controlling devices of the supporting post having their parts in the positions corresponding to f the inclined position of the platform in accordance with Fig. 3 and during the ascending of said platform.

In the drawing, I designates a supporting frame, bridge or platform for lifting load-s, for

linstance a motor car. The platform is supported plunger space 5 contain liquid and are interconnected Yby conduits 6 and 1. Inserted between.

If the kEach of these sup.

is supplied to the plunger, liquid flows from the plunger into the cylinder through conduit 6,

the ycontrolling device and conduit l, and that-YY both the plunger and the platform are lifted. Conversely, when air escapes from the hollow plunger, liquid will return from the cylinder into the plunger and the latter will descend.

The controlling device 8 (Fig. 2) substantially consists of two valves mounted in series' intermediate conduits 6 and 1. The conduit II connecting the tubes 6 and I is split up, intermediate the two valves, into two parallel passages I2 and i3. The first valve, as seen in the direction in which liquid is supplied tothe cylinder space E, consists of two cylindrical slide valves I4, I mounted on a common shaft, of which valves one (I4) is exposed on its outer face to the pressure of the liquid in the controlling device (i. e. substantially to the pressure of the liquid in the cylinder space Il), and the other confines, by the outer face of' its piston, a chamber communicating with the air branch III so as to be exposed to the pressure in the plunger. In order to obtain a sufficient difference of pressure between the cylinder space I! and the plunger space 5 duringv movement of the plunger, an adjustable throttle ItV is inserted before the first valve in theA connecting conduit It. The cylindrical slide Valves I4, 5 are adapted respectively to close and to open the passagesl2 and I3'. The valves I4, t5 are maintained in central positions by press-ure springs Il and t8 as long as the forces exerted on the piston faces of the valves are equal. The second valve is also constituted as a cylindrical slide valve I9 having a circular rowV of openings isa, two of which are shown in Fig. 2. Said valve i-s .connected to the platform by a rod 2!V and a lever ZI so as to be actuated whenever the platform alters? its position with respect to the plunger. This slide valve controls the cross sectional area of each of the passages I2, I3; The controlling device operates as follows: During the raising movement of the platform, liquid is driven, by compressed air, from thev plunger through conduit Ei, controlling device and conduit 'i to the cylinder space It. In that Y case the pressure in the air duct Q is of' course higher than that in the rcylinder so that the slide Valves I4, I5 of the rst valve are lifted, passage I2 is opened and passage I3' is closed (Fig. 2l.

Consequently, under these conditions only the passage I2 serves for the control. The cross sectional area of this passage is controlled by the second' valve in dependency of the position of the platform. Ii', during the raising movement, the corresponding supporting post lags' behind the other supporting post, the platform will assume the inclined position shown in Fig. l and the valve |79 will he forced down so as to fully open the passage I2 (Fig. Z). It will be apparent that the full opening of passage I2 will have effeet only when the cross-sectional dimension of all openings ma together is larger than that of passage I2.

In the other supporting post, however, the valve I9 will be lifted by the inclined position of the platform, so as to close passage I2. The

result of this controlling action is that the supporting post, which is lagging behind, is supplied with an appreciable amount of liquid, whereas hardly any liquid is supplied to the supporting post that is raised too rapidly. Consequently, the platform resumes its horizontal position.

In Figs. 3, 3a and 3b is illustrated what happens when in the above mentioned case the platform is ascending in an inclined position. Assuming the left hand: supporting post to lag behind the right hand supporting post, slide valve I9 of the first mentioned supporting post will be forced down so as to open passage I2 to a degrecV corresponding with the inclination of the platform (Fig. 3a), While slide valve I9 of the second supporting. post will be drawn upwards so as to close passage I2 to a greater or less extent (Fig. 3b). The result thereof is that the supply of liquids to the lagging supporting post is increased, while that of the other supporting post is decreased,

During the descending movement, the reversel takes place. In that case, the pressure irl-'the` cylinder 2 exceeds that in the airduct 9, so that the valves I4, I5 are forced down, passage t3 isv opened and passage f2 closed. The slide valve Ie of the second valve then controls the cross section-al area of passage I3, in such manner that, if the descending movement isv too rapid or too slow, the discharge of liquid from the cylinder is reduced or fully checked, or increased, respec- I tively.

When the platform is ascending or descend- I ing in an exactly horizontal position the valves I9- of the two controlling devices 8 are placed in equal positions relative to the corresponding passages I2 and leave the latter half opened.

A In order that,A in case of rupture of a conduit, for instance of the airduct 9, the corresponding supporting post would not descend, the controlling device comprises a check valve 22 maintained in its open position by an adjustable spring 23, but closing automatically if the pressure in conduit 6 is lower than that in conduit T and the difference of pressure exceeds a certain value.

This check valve also restricts the velocity at which the platform can descend.

When the platform is carried by three or VfourV supporting pos-ts, a very accurate control is obtained if the levers controlling the valves i9 point it is necessary that the cross sectional area of the non-controlled connecting conduit of the central supporting post substantially equals the maximum cross sectional area of the connecting conduit of each of the other supporting posts.

It is not necessary that each control device be mounted on its individual post.. For instance,

two control devices forming a single unit, may

be mounted on one supporting post. Instead of compressed air, liquid may be sup plied or discharged through conduit 9, so thatinstead of a pneumo-hydraulic system a purelyv hydraulic system is obtained.

The throttle I6 can be omitted when the cross sectional area of conduit 6 is restricted". The pro` vision of a throttle has, however, the advantage that said member can be easily adjusted.

Attention is drawn to the fact that the springs II, I8 for returning the slide valves I4, I5 to their central positions may be omitted. In that case, the terminal positions of the valves, in which one of the passages I2, I3 is open and the other closed, should be defined by abutments.

What I claim is:

1. A raising platform or lift, particularly for lifting a load such as a motor vehicle, comprising at least two supporting posts, a reservoir adapted to contain uid under pressure, and for each of said posts a cylinder and a piston adapted to move said post hydraulically, a pressure fluid conduit connecting said cylinder to said reservoir and two valves constituting a device for controlling the pressure fluid within said conduit and for maintaining the platform automatically in a horizontal position, one of said valves being operated by the difference of pressure obtaining at two points in the pressure fluid system, the other valve being operated in dependency of the position of the platform relative to the corresponding supporting post, and the part of said fluid conduit intermediate the two valves including two branches, one of which is closed during upward movement and the other during downward movement of said post by the rst mentioned valve, the cross-sectional area of the other branch being controlled by the second valve.

2. A raising platform or lift as claimed in claim 1 in which the piston of each of -said supporting posts is constituted as a hollow plunger, the plunger space communicating with the working space of the corresponding cylinder through a liquid conduit, in which the controlling device inserted,

3. A raising platform according to claim 1 in which the piston of each of said supporting posts is constituted as a hollow plunger, the plunger space communicating with the working space of the corresponding cylinder through a liquid conduit, in which the controlling device, being mounted on top of the plunger of the corresponding post, is inserted.

4. A raising platform according to claim 1 in which the piston of each of said supporting posts is constituted as a hollow plunger, the plunger space being partially lled with liquid and connected, at a, level above that of the liquid, to a compressed air conduit, the Working space of the corresponding cylinder communicating with said plunger space through a liquid conduit, in which said controlling device, being mounted on top of the plunger of the corresponding post, is inserted, and said first mentioned Valve being exposed on one side to the pressurein a point of the liquid conduit, on the other side to the pressure in a point of the air-duct.

HERMAN VOSKAMP.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 955,852 Coyle Apr. 26, 1910 1,962,924 Bristol June 12, 1934 FOREIGN PATENTS Number Country Date 484313 Germany --f-f---T'sv 9ct" 15? 

